Apparatus for providing a progression or succession of chords available for a given melody were known. Such apparatus have been built in electronic music instruments.
Japanese patent application laid open to public as Sho No. 58-87593 discloses an apparatus of this kind which comprises the following means in order to determine chords for a melody:
(a) first implicit means assumes that a given melody always has a single key;
(b) second implicit means assumes that a given melody always ends on a resolution point such as a tonic or key;
(c) key determining means, which is operable based on the above assumptions, determines a key of the given melody, the determined key being represented by a pitch or pitch class (e.g., A, B, C) indicative of a tonic or key note and a mode (either major or minor);
(d) chord generator means generates seven diatonic chords from the determined key because third implicit means assumes that a given melody is always a diatonic melody which implies diatonic chords;
(e.g., for C major key, seven diatonic chords are triads of C major, D minor, E minor, F major, C major, A minor and B diminished);
(e) for each bar of the given melody, matching means evaluates a degree of matching between pitch or pitch class content of each of the seven diatonic chords and that of a melody bar of interest; and
(e.g., for a diatonic chord of triad C major, the pitch content thereof is given by C, E and G);
(f) a chord transition table stores fixed transition probabilities (weights) each from one diatonic to the next diatonic chord;
(g) for each of the seven diatonic chords, multiplication means multiplies a degree of matching (evaluated by the matching means) by a corresponding weight (supplied from the transition table) to obtain a product;
(h) for each bar of the melody, selecting means selects one of the seven diatonic chords from the chord generator means with respect to a bar of interest such that the selected diatonic chord has the maximum product among those seven diatonic chords.
Another prior art apparatus for producing a chord succession available for a given melody is disclosed in U.S. Pat. No. 4,539,882. This apparatus comprises the following means:
(a) first implicit means assumes that a given melody has always a single key;
(b) second implicit means assumes that a given melody always ends on a resolution point such that the pitch of the last melody note must be a member of a tonic chord;
(c) under the above assumptions, key determining means determines a key specific to the given melody;
(d) third implicit means assumes that a given melody always starts with a tonic tone or a member of a tonic chords;
(e) for each bar of the presently given melody, important or conspicuous tone evaluation means evaluates one or more important melody tones contained in a bar of interest;
(f) using the third assumption, the important tone(s) and the detemined key, a chord is selected for the first bar of the currently given melody;
(g) table means is provided which returns a selected chord for a current bar in response to the selected chord for the preceding bar and important melody tone(s) in the current bar; and
(h) for each successive bar of the given melody, table access means references the table means using the selected chord for the preceding bar and the evaluated important melody tone or tones in the current bar whereby a chord is selected or determined per bar.
As noted, either of the prior art apparatus implicity takes several assumptions or constraints on a melody to be analized. One constraint requires that a melody for analysis must be relatively long, ending with a predetermined point (resolution point). Another requires no change of key (modulation) in the course of a melody under analysis. Third requires that only particular family of chords such as diatonic chords are assumed for a melody for analysis. Although a melody in general can suggest more than one harmonic interpretations, because of the nature of music, either prior art apparatus only provides a single succession or progression of chords for a melody. Further, none of the prior art apparatus contemplates a temporal order, series, succession or stream of melody notes in a melodY in bar. It is a characteristic of the nature of music that with a first melody suggesting a set of chords, a second melody, which has the same or similar pitch content of the first melody but a different order, succession of melody notes from the second (i.e., the first melody wave is different from the second), can suggest a different set of chords.
The present invention is provided to overcome these problems.